Field of the Invention
The present invention relates to a sensor device represented by a photoelectric sensor and a method of producing the same.
Description of the Background Art
A sensor device represented by a photoelectric sensor has various components accommodated inside a casing. In that case, there is a case in which an assembly structure is adopted such that the casing is composed of a body case in the form of a box and a body cover in the form of a flat plate, and the various components are accommodated inside the body case via an opening provided through the body case and subsequently the body cover is assembled to the body case to cover the opening. Note that when this assembly structure is adopted, then, in order to seal a space in the casing from outside to ensure resistance to an environment, the body case and the body cover are often welded and thus bonded together.
For example, Japanese Patent Laying-Open No. 2009-170133 discloses a photoelectric sensor in which a body case has a side surface provided with an opening, a step is further provided at a portion of the body case located at a peripheral edge of that opening, a body cover is fitted to the step, and a laser beam is radiated along an outer periphery of the body cover to straddle an end surface of the body cover and an end surface of the above step of the body case to weld and thus bond the body case and the body cover together.
When this assembly structure is adopted, the end surface of the body cover and the end surface of the above step of the body case opposite thereto mutually melt together so that an externally molten metallic material fills a gap between these end surfaces and furthermore, the material is cooled and thus solidified to form a welded portion at a position close to the end surface of the body cover.
When the above assembly structure is adopted, it is necessary to radiate a laser beam to straddle the end surface of the body cover and the end surface of the above step of the body case, as has been described above, and accordingly, when the precision of the body cover and body case as parts is taken into consideration, it is necessary to make the laser beam's spot diameter large to a corresponding extent.
However, when the laser beam's spot diameter is thus made large, then, unless the laser beam's power is accordingly increased, causing the metallic material to be externally molten is not ensured, and accordingly, not only is large-scale laser equipment required but the laser beam's irradiation would also significantly increase the casing's temperature, and as a result there is also a possibility that there may be a negative effect on a component e.g., of resin, rubber, etc. previously assembled to the casing.
In order to solve this, it is necessary to strictly manage the body case and the body cover in precision as parts, and also suppress an increase in temperature of the casing by using various heat dissipating jigs, and furthermore, carefully perform laser irradiation under a strict condition. This serves as a cause of a significantly tightened production cost.